Prosthetic heart valves are used to replace damaged or diseased heart valves. In vertebrate animals, the heart is a muscular organ with four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. Prosthetic heart valves can be used to replace any of these naturally occurring valves, although repair or replacement of the aortic or mitral valves is more common since they reside in the left side of the heart where pressures are the greatest.
A conventional heart valve replacement surgery involves accessing the heart in the patient's thoracic cavity through a longitudinal incision in the chest. For example, a median sternotomy requires cutting through the sternum and forcing the two opposing halves of the rib cage to be spread apart, allowing access to the thoracic cavity and heart within. The patient is then placed on cardiopulmonary bypass which involves stopping the heart to permit access to the internal chambers. Such open heart surgery is particularly invasive and involves a lengthy and difficult recovery period.
Minimally invasive surgical techniques are evolving, where a valve prosthesis can be introduced into a patient using a catheter that is introduced via a small incision that provides access to, for example, a femoral artery or the heart. A major issue during heart valve replacement is positioning the prosthetic valve within a small, approximately 2-5 mm, range at the target site. Medical doctors have tried a variety of methods to confirm their judgment during heart valve replacement procedures, including various marking systems, contrast dye injections multiple times along the procedure, and viewing angle adjustments in the imaging systems. However, there are limitations with these methods and the current imaging systems. For example, the standard error of the current imaging systems is about 2 mm, and operator handling introduces additional variability. Furthermore, heart movement by itself can shift the target landing site by 2-5 mm. All these make it very difficult to land a prosthetic valve accurately.
Another critical issue with sutureless valves is valve migration. For example, when an aortic prosthetic valve is deployed, 100-200 mmHg pressure loads on the aortic valve immediately. The pressure times the valve surface area produces a substantial load force on the prosthetic valve and can cause valve migration towards the aortic arch. The other cause of valve migration is tilted valve landing. When tilted, the prosthetic valve will have a larger surface area facing the blood flow, which could push the prosthetic valve into the aorta.
There remains a need in the art for improved valve prosthesis and delivery devices for introducing a valve prosthesis into a patient.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.